Titanium flanged alumina ceramics vacuum duct with low impedance

We successfully developed alumina ceramics vacuum ducts for the 3GeV-RCS of J-PARC at JAERI. This duct has titanium flanges and exterior RF shield to reduce duct impedance. The temperature of titanium flange became 45 °C due to eddy current heating under dipole magnet operation. The longitudinal duct impedance was sufficiently small for stable beam acceleration as shown by impedance measurement by the coaxial method. It was found that the radiation damage of the capacitor used for the RF shield of this duct was small, because the capacitance decreased only by 7% after a gamma-ray irradiation of 30 MGy. This duct is usable for the 3GeV-RCS of J-PARC.